Latch needle having a stepped saw slot

ABSTRACT

The latch needle according to the invention is provided with a latch slot with profiled inside areas of the cheeks. A latch is positioned inside this latch slot, for example with the aid of a rivet. The inside areas of the cheeks that immediately surround the rivet guide the latch on the side and together with the latch define a small play, thus resulting in a precise positioning. The remaining latch slot area can be wider to reduce the latch friction at the latch slot as much as possible.

BACKGROUND OF THE INVENTION

The invention relates to a latch needle, in particular for knittingmachines, with the features as listed in the preamble to patent claim 1.

Latch needles are used for different types of knitting machines in use.A latch needle is known, for example, from German Patent 1113537. Thelatch needle has a needle body with a hook formed onto its end. A latchslot is formed near the hook, in which a latch is positioned so as topivot. The latch slot cheeks and the side surfaces of the latch shankfunction to guide the latch on the side. As a result, the latch can restwith its free end, the so-called latch spoon, on the hook tip and canthus close off the trapping clearance. From this closed position, thelatch can pivot back to the latch upright position, in which it freesthe trapping clearance. A rivet or pin ensures the pivoting positioningof the latch.

The pivoting movement should be as easy as possible. Modern knittingmachines often require needles with extremely easy-moving latches, whichshould also be guided with the highest possible precision. The easymovement should be ensured for new needles as well as old ones. Needleswith hard-to-move latches knit irregularly and thus create a poor looppicture.

The latches of some machines must return during the knitting operationto the upright position as a result of their own weight. If this doesnot happen reliably, the danger exists that the latches come in contactwith machine parts, e.g. the yarn-feed apron, and are thus bent.

The easy movement of the latch can be achieved with increased latchplay. Dirt, fiber residues and the like, which enter the latch slot, canconsequently cause fewer problems for the smooth running of the latch.The increased latch play, however, worsens the latch guidance even ifthe needle is still new because the needle latch spoon can no longer hitthe hook precisely and thus cannot reliably close off the yarn trappingclearance. With increasing wear, the latch guidance becomes more andmore difficult, which in turn can reduce the operational reliability.

A different problem is caused by the increased latch play if the latchis positioned with rivets punched out of the slot cheeks, as disclosedin U.S. Pat. No. 1,991,140. The latch that is provided with a pivotingopening is inserted into the latch slot to position the latch. Followingthis, portions of the slot cheeks are subsequently pressed or punchedtoward the inside with the aid of two pressure feet (plunging tools),such that these enter the pivoting opening for the latch and form apositioning rivet for the latch. This operation requires relativelylittle latch play. In particular with the area surrounding the pivotingopening, the latch forms an abutment for the pressure or punchingoperation. If the latch is noticeably smaller than the latch slot, aprecise positioning of the latch for the punching or pressing operationis not possible. As a result, the latch needle possibly cannot beproduced with the desired quality.

During the latch closing movement, the thread or a yarn glides along thesurface of the latch slot cheeks, driven by the underside of the latchshank, and into the hook clearance. In the process, the problem of thethread being damaged by sharp edges of the latch slot or the latch shankoccurs with increasing frequency and, in the extreme case, can lead to abreak in the thread.

Another problem that can occur with increased play between latch shankand latch slot is that the thread is caught between the latch shank andthe cheek of the latch slot. This reduces the easy mobility of the latchand can even lead to the needle becoming totally inoperable.

Starting with this, it is the object of the invention to provide a latchneedle with a precisely guided, easy moving latch.

SUMMARY OF THE INVENTION

The above object generally is achieved by a latch needle having thefeatures according to the present invention.

The latch needle according to the invention is provided with a latchslot that is delimited by two cheeks, the insides of which arepositioned opposite each other. The inside surfaces of the cheeks arerespectively divided into at least two surface regions, one of which islocated directly adjacent to the pivoting mechanism and thus forms apivoting surface. This surface area advantageously surrounds thepivoting mechanism and functions to guide the latch on the side, thuslimiting its pivoting play on the side. The other surface area ispositioned at a distance to the pivoting mechanism and defines acomparably larger slot width. The cheek is recessed, so-to-speak, inthis surface area so that a clearance develops between the latch shankand the latch slot cheek, which promotes the easy movement of the latch.The clearance that develops between the latch shank and the cheek cantake up fiber filaments without this essentially reducing the easymovement of the latch. Threads, fibers or filaments and dust inparticular can thus be prevented from being caught between the cheek andthe latch shank.

The latch needle according to the invention combines improved latchguidance with decreased frictional resistance and additional clearancespace for fibers and filaments.

This applies in particular if the measure according to the invention isnot used on one cheek only, but on both cheeks. The resulting latchneedle is symmetrical relative to a center plane on which the pivotingaxis of the latch is positioned perpendicular. With this latch needle,the frictional resistance of the latch is reduced on both sides.

For the needle according to the invention, the latch slot width isnarrower in at least one location near the pivoting mechanism than in atleast one other location, at a longer distance thereto. An edge, a stepor a curved section can be used as transition between the correspondingsurface areas on the cheek inside. The edge between the two surfaceareas can be either sharp or round. The surface areas can have a flat orarched design. In particular, the surface area that is arranged at adistance to the pivoting mechanism can be curved.

Whereas the cheek surface areas, which define a narrow slot width, areformed at the pivoting mechanism or around it, the other surface areasare preferably located at the area where the slot ends and follow theneedle outline, for example the needle top surface. The surface areas inthat case can form a strip that adjoins the area where the slot ends.Alternatively, the respective cheek surface area can be recessed andshaped in such a way that a projection is formed on both sides of thelatch shank at the respective cheek, which serves the same purpose as awasher arranged on the rivet. These projections center and guide thelatch in the center of the latch slot.

The pivoting mechanism for the latch needle preferably is a continuousrivet, but can also be a divided one. The latter can be produced in thatportions of the cheek are pushed into a latch opening during a reshapingprocess. The rivet can be produced by punching it out of the cheek or byinserting a separate pin.

The tongue play on the side advantageously amounts to only a few1000^(th) millimeters, e.g. approximately 0.02 millimeters or less, nearthe pivoting mechanism. In contrast, the latch play in the expandedlatch slot region (other surface areas) is noticeably higher, forexample more than 0.03 millimeters. A sufficiently large slot orclearance space is thus created between the side surfaces of the latchand the cheek insides. This gap or clearance can be uniformly wide orcan be shaped in the form of a wedge and preferably extends over atleast a portion of the latch pivoting range. The gap or clearance can bedivided into sections that can extend, for example, from the pivotingend positions to near the area of the pivot. To facilitate the completereturn of the latch to the upright position, the expanded latch slotregion can also extend further to the location where the latch isstanding upright.

Additional advantageous details of the invention follow from thesubsequent description, the drawing or the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are illustrated in the drawingand show in:

FIG. 1 A latch needle in a perspective and schematic representation,showing details.

FIG. 2 The latch needle shown in FIG. 1, in a partial section view fromthe side and showing details.

FIG. 3 The latch needle according to the FIGS. 1 and 2, shown ascross-sectional and detailed view on a different scale.

FIG. 4 A modified embodiment of the latch needle as cross-sectionalrepresentation, in a simplified view.

FIG. 5 A modified embodiment of the latch needle as cross-sectionalrepresentation, in a simplified view.

FIG. 6 A different modified embodiment of the latch needle, in a partialsectional and schematic view from the side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a basic design of a latch needle 1. The latch needle 1 hasa needle body 2 with a hook 3 formed onto its free end. The hook ends ina hook tip 4, which functions as counter stop and support for a latch 5that is positioned pivoting on the needle body 2. A latch slot 6, whichis delimited by two cheeks 7, 8, is formed into the needle body 2 foraccommodating the latch 5. The cheeks 7, 8 are respectively designedmirror-symmetrical to each other and are arranged parallel to eachother.

The latch 5 has a latch shank 11, which projects with one end 12 intothe latch slot 6. FIG. 2 in particular shows that the end 12 is providedwith a latch opening 14 for positioning the latch 5. At the opposite end15, the latch 5 has a latch spoon 16 with a recess 17 (noucat) on thehook side. The present embodiment is a needle with noucat latch.Alternatively, a noucat can be provided in the hook 3 or its hook tip 4,into which a correspondingly tapered section of the latch 5 fits. In theclosed position (FIG. 2), the latch 5 closes off the hook clearance 19.

According to FIG. 3, the latch 5 is positioned pivoting inside the latchslot 6 with the aid of a rivet 18, consisting of two rivet halves 18 a,18 b. FIG. 3 also illustrates that the rivet halves 18 a, 18 b areformed by wall sections of the cheeks 7, 8, which sections are pressedwith a pressing or punching technique from these cheeks and into thelatch opening 17 [sic].

The latch 5 has two side surfaces 21, 22, which can be formed level andparallel to each other. If necessary, the side surfaces 21, 22 can alsobe oriented at an angle toward each other, so that the latch 5 has anapproximately wedge-shaped design. The side surfaces 21, 22 can be flat,curved, stepped or have other outlines. It is preferable if the latch 5is designed symmetrical to a center plane, on which a pivoting axis S,determined by the rivet 18, is arranged perpendicular.

The cheeks 7, 8 are also symmetrical to this center plane, as indicatedby the dash-dot line E in FIG. 3. The following description of the cheek7 therefore also applies to the cheek 8.

The inside area of cheek 7 is subdivided into two surface areas 23, 24.The surface areas 23, 24 are separated and determine different slotwidths. The surface area 24 is arranged immediately adjacent to thepivoting mechanism formed by the rivet 18. In particular in the regionof the pivoting mechanism, meaning the rivet 8 [sic], it determines aslot width that is only slightly wider than the width of the latch 5 atthis location. Thus, a pivoting gap 25, 26 of only a few 1000^(th)millimeters is formed at the pivoting mechanism, on both sides of thelatch 5. The pivoting play determined by both pivoting gaps 25, 26, forexample, is limited in this case to 0.02 mm.

On the other hand, the surface areas 23 determine a comparatively widerslot width in that the surface areas 23 change via a step 27 over to thesurface areas 24, as shown in FIG. 3. A gap 28, 29 consequently resultsbetween the respective side surface 21, 22 of latch 5 and the surfacearea 23. The average or median width of this gap is wider than theaverage or median width of the pivoting gap 25, 26. The gap depth isdetermined by the height of the surface area 23. The height of surfacearea 23 (measured between needle top 31 and opposite arranged needleback) is advantageously higher than half the distance between thepivoting rivet 18 and the needle top surface. The thickness of the cheek7, 8 can serve as alternative reference for the depth of the recess. Theheight of surface region 23 is preferably higher than this depth, thusmaking it possible to achieve the desired ease of movement and thedesired precision.

The latch needle 1 described in the above operates as follows:

During the operation, the latch needle 1 performs a back and forthmovement, during which the needle body 1 moves back and forth along itslongitudinal direction. The latch 5 in the process performs aback-and-forth moving pivoting movement around the pivoting axis S, froma closed position shown in FIG. 2, via an intermediate positionaccording to FIG. 1, into an upright position and back. Starting withthe upright position, the thread driven by latch shank 11 glides overthe top surfaces 9, 10 of cheeks 7, 8 and into the hook clearance 19.

The latch needle 1 described so far consequently exhibits improvedknitting behavior.

As shown in FIG. 3, the end 12 of latch 5 for latch needle 1 is guidedon the rivet 18 inside the latch slot 6. In the ideal case, the latch isguided only by the surface areas 24 of cheeks 7, 8, but not the surfaceareas 23. The latch shank 11 insofar is positioned freely inside thelatch slot 6 and in particular does not make contact with the surfaceareas 23. The end 12 of latch 5 is guided by the surface areas 24 withsuch precision that the latch spoon 16 hits the hook 3 or the hook tip 4with only a slight center deviation. The precise guidance of latch 5represents a wear reserve, meaning even if the play on the side of latch5 increases with increasing wear, it still remains within permissibletolerances. The recessed surface areas 23 with gaps 28, 29 createclearances, which prevent or reduce any hindrance of the latch 5movement, even if oil, fiber residues or dirt are deposited along theside surfaces 21, 22 of latch 5 and/or the inside areas of cheeks 7, 8.

The precise guidance of the latch 5 near the pivoting mechanism by thesurface areas 24 prevents a contact between the side surfaces 21, 22 oflatch 5 and the surface areas 23, even if the pivoting play of the latch5 increases somewhat following a longer period of operation by the latch5 and the start of wear.

The latch slot 6 of one preferred embodiment of the invention extendsthrough the needle body 2, as shown in FIG. 2, and is open on the top(needle top 31) as well as the back. The area on the needle top wherelatch slot 6 ends is widened through an additional milling or stamping,which creates the step 27 and the surface areas 23. The surface area 23consequently extends from one end 32 of the hook across a center region33, located approximately above the pivoting mechanism, to an end region34, occupied by the shank 11 of latch 5 when in the upright position. Asa result, this surface area 23 extends nearly over the complete pivotingrange of latch 5. Owing to this special design of the surface area 23,the latch 5 is guided precisely, in particular in the closed positionand the upright position because the shank 11 of latch 5 thus entersdeeper into the narrower latch slot region defined by the surface areas24. In the final analysis, this is achieved in that the surface area 23with an approximately constant width follows the outline of the needletop surface 31.

Alternatively, the shape of surface area 23 can deviate from the stripshape, so that the step 27 no longer follows the outline of the needletop surface 31. Also, the surface area 23 can be divided into partialsurface areas 23 a, 23 b, for example as shown in FIG. 6. As a result,it is possible to combine a far-reaching reduction in the latch frictionwith a precise positioning and guidance.

FIG. 4 shows that for one alternative embodiment, for which the surfaceareas 23, 24 can be designed according to FIG. 2 as well as FIG. 6 orcan have a different design, an edge 37 is provided in place of the step27, which separates the surface areas 23, 24. For reasons of clarity,the pivoting mechanism is not shown in FIG. 4 and is only symbolizedwith the aid of the pivoting axis S. This mechanism can be either a pinor a rivet. The surface areas 23, 24 are essentially flat, as for theexemplary embodiment in the above. However, in contrast to theaforementioned embodiment according to FIG. 3, they are not arrangedparallel to each other in this case (FIG. 4). The surface areas 23 forma funnel-shaped expansion of the latch slot 6 in the direction of theneedle top surface 31. The gaps 28, 29 thus become wedge-shaped, whereinthe gap width is larger at least in the area where the latch slot 6 endsthan the distance between the surface areas 24. The average gap width,which can be measured approximately in the center of the surface region23, is preferably noticeably larger, meaning by a few 1000^(th)millimeter, than the gap width between the surface areas 24.

As shown in FIG. 5, the surface areas 23 can also have a curved designor can transition with a curvature to the surface areas 24. This alsoresults in a funnel-shaped expansion of the latch slot 6, which reducesthe friction of latch 5, wherein the surface areas 24 ensure anexcellent guidance of the latch. These areas are preferably planarsurfaces that enclose the rivet 18.

The latch needle 1 according to the invention is provided with a latchslot 6 with profiled inside surfaces of the cheeks 7, 8. A latch 5 ispositioned inside the latch slot 6, for example with the aid of a rivet18. The inside areas of cheeks 7, 8 that are located immediatelyadjacent to the rivet 18 function to guide the latch 5 on the side andwith this guidance define an insignificant play. The latch is preciselypositioned in this way. The remaining latch slot 6 can have a largerslot width to reduce the latch 5 friction inside the latch slot 6 asmuch as possible.

What is claimed is:
 1. A latch needle comprising: a needle body with alatch slot formed therein, which is delimited by inside areas of twoopposite-arranged cheeks and ends at a top surface of the needle body; alatch with a latch shank that extends into the latch slot and isprovided with a latch opening; and a pivoting mechanism arranged insidethe latch slot, with which the latch is positioned inside the latchslot, such that the latch can pivot between a closed position and anupright position; and wherein at least one of the opposite-arrangedinside areas is divided in separate surface areas, one of which isarranged near the pivoting mechanism and the other one at a distance tothe pivoting mechanism and the slot width of the latch slot that isdelimited by the surface areas at a distance to the pivoting mechanismis wider than the slot width delimited by the surface areas that areadjacent to the pivoting mechanism, and the clearance between thesurface areas at a distance to the pivoting mechanism and flanks of thelatch shank are greater than the clearance between the flanks of thelatch shank and the surface areas that are adjacent the pivotingmechanism.
 2. A latch needle according to claim 1, wherein both cheeksof the latch needle are divided into separate surface areas.
 3. A latchneedle according to claim 1, wherein a line-shaped or strip-shapedseparation area is formed between the surface areas in order to separatethese areas.
 4. A latch needle according to claim 1, wherein a step isformed as a separation area between both surface areas in order toseparate these areas.
 5. A latch needle according to claim 1, wherein anedge is formed as a separation area between both surface areas in orderto separate these areas.
 6. A latch needle according to claim 5, whereinthe edge is rounded.
 7. A latch needle according to claim 3, wherein theseparation area is follows the outline of the needle top on the sidewhere the latch projects from the latch slot.
 8. A latch needleaccording to claim 1, wherein the separation area has a curved shape. 9.A latch needle according to claim 1, wherein the surface area that isremoved from the pivoting mechanism forms an end area of the latch slotthat is expanded.
 10. A latch needle according to claim 1, wherein thesurface area that is removed from the pivoting mechanism extends atleast into an area occupied by the latch in the closed position.
 11. Alatch needle according to claim 1, wherein starting with the needle top,the surface area that is removed extends into the latch slot by adistance that is greater than half the distance between the needle topand the pivoting mechanism.
 12. A latch needle according to claim 1,wherein the depth of the recess determined by the surface area at leastequals the wall thickness of the respective cheek.
 13. A latch needlecomprising: a needle body with a latch slot formed therein that isdelimited by inside areas of two opposite-arranged cheeks and ends at atop surface of needle; a latch with a latch shank that extends into thelatch slot and is provided with a latch opening; and, a pivotingmechanism arranged inside the latch slot and with which the latch ispositioned inside the latch slot such that the latch can pivot between aclosed position and an upright position; and wherein at least one of theopposite-arranged inside areas is divided in separate surface areas, oneof which is arranged near the pivoting mechanism and the other one at adistance to the pivoting mechanism and the slot width of the latch slotthat is delimited by the surface areas at a distance to the pivotingmechanism is wider than the slot width delimited by the surface areasthat are adjacent to the pivoting mechanism; and wherein an edge isformed as a separation area between both surface areas in order toseparate these areas, and the edge is rounded.
 14. A latch needlecomprising: a needle body with a latch slot formed therein that isdelimited by inside areas of two opposite-arranged cheeks and ends at atop surface of needle; a latch with a latch shank that extends into thelatch slot and is provided with a latch opening; and, a pivotingmechanism arranged inside the latch slot and with which the latch ispositioned inside the latch slot such that the latch can pivot between aclosed position and an upright position; and wherein at least one of theopposite-arranged inside areas is divided in separate surface areas, oneof which is arranged near the pivoting mechanism and the other one at adistance to the pivoting mechanism and the slot width of the latch slotthat is delimited by the surface areas at a distance to the pivotingmechanism is wider than the slot width delimited by the surface areasthat are adjacent to the pivoting mechanism; and, wherein a separationarea formed between the surface areas in order to separate these areashas a curved shape.